On Thu, Feb 28, 2013 at 07:24:28PM +0000, Luke Kenneth Casson Leighton wrote:
> On Thu, Feb 28, 2013 at 3:14 PM, Lennart Sorensen
> <lsorense@csclub.uwaterloo.ca> wrote:
>
> > There is no need to do things 500 different ways.
>
> lennart: you've fundamentally misinformed of the reality of the ARM
> hardware development world. there are over 600 ARM licensees,
> world-wide. automatically therefore you're above the threshold
> number that you arbitrarily picked.
>
> additionally, each hardware device that uses any one of the products
> created by any one of those 600+ licensees *will*, by the very nature
> of that hardware design having hard-wired interfaces, be completely
> and utterly different from any other device. GPIO20 for example could
> be used to power on a WIFI module on one device, and could be
> disconnected or used via a multiplex option as an SD card's clock
> line.
>
> if you look at the xanadux source code (on sourceforge) when i was
> working on the reverse-engineering of HTC wince phones, we had *OVER
> 250* source code files added which covered i believe it was 9 new
> hardware platforms for the PXA25x and PXA27x series [before marvell
> bought the intel pxa architecture]
>
> russell bless him asked us to flatten these out to a single
> directory. the number of files to be added was *double* that of the
> total existing number of files that had ever been contributed up until
> that point.
>
> even with 5 of us working and coordinating closely for about eighteen
> months on those 9 products, it was virtually impossible for us to
> generate any kind of significantly common code.
>
> all that devicetree has done is move the problem, as well as add a
> runtime overhead to the execution of resource-critical devices.
>
> not very clever, that.
The GPIO line use is a bit of a problem. Almost makes you wish for a
firmware thing like ACPI to abstract such hardware details away from
software. Almost but not quite. Of course some of that stuff does get
covered by information in the devicetree.
Of course it would seem that if the HTC phones are that different from
each other while doing essentially the same things, then the hardware
designers are designing them wrong. If they don't have to be different,
then they shouldn't be different.
--
Len Sorensen